Dynamic rollover threshold of articulated freight vehicles

Different measures of relative roll instability of heavy vehicles are investigated to determine their dynamic rollover characteristics. Analytical models of different vehicle combinations are presented and a concept of effective lateral acceleration is proposed to characterize the relative roll instability under dynamic directional manoeuvres. The analytical models for a five–axle tractor semi–trailer combination and an eight–axle A–train double are analysed to establish the dynamic rollover threshold based upon relative roll instability criterion and effective lateral acceleration. The dynamic rollover threshold of the vehicle, derived for different suspension properties and operating conditions, is compared with the corresponding static rollover threshold of the vehicle. From the results of the study, it is established that dynamic rollover threshold based on effective lateral acceleration in most cases is either slightly lower or equal to the static rollover threshold acceleration. The difference between the dynamic and static rollover thresholds is less than 5% for the vehicle configurations and the steering manoeuvres considered in the study. The static rollover threshold may thus be conveniently employed to estimate the dynamic rollover propensity of heavy vehicles.